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PALAEONTOLOGY OF NEW-YORK. 
Orthoceras perst datum (n. s.). 
Plate LXXII. Fig. 3. 
Shell rapidly tapering; outer chamber large : septa distant from one- 
fourth to one-third the diameter of the shell. 
Surface strongly striated longitudinally : transverse striae ? 
This species is marked by its rapid attenuation and strong longitudinal striee. 
Fig. 3. A fragment preserving part of the outer chamber and several of the chambers above, 
from which the shell is partially exfoliated. 
Geological position and locality. In the slialy limestone of the Lower Helderberg 
group : Schoharie, Schoharie county. 
Orthoceras nulls (n. s.). 
Plate LXXII. Fig. 4 a, b. 
The specimen is a cast, consisting of about eleven chambers. The septa are more 
distant and less convex than in O. longicameratum , and the shell more robust. 
Fig. 4 a. The fragment, which is somewhat flattened from pressure. 
Fig. 4 b. A section showing the subcentral position of the siphuncle. 
Geological position and locality. In the central portion of the Lower Helderberg 
group : Schoharie. 
Orthoceras pauciseptum (n.-s.). 
Plate LXXII. Fig. 5 a, b. 
Shell cylindrical, very gradually tapering : septa extremely distant : 
siphuncle excentric. Surface unknown. 
The specimen is a fragment, remarkable for the deep chambers which distinguish 
it from any other species in this geological period. 
Fig. 5 a. A fragment of this species. The lower chamber is cut longitudinally, to show the 
place of the siphuncle. 
Fig. 5 b. Transverse section, showing the excentric position of the siphuncle. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Schoharie. 
